Problem with Query and Entity.Attribute("...").In(array)

Hi Guys,

  I'm unsure if this is a bug or if I am doing something wrong, but when using code like the following...

var someIds = new List<int> { 1, 2 };
            using (var uow = ModelUnitOfWorkFactory.Create())
            {
                var toUpdate = new Query
                {
                    EntityType = typeof(MyTable),
                    QueryExpression = Entity.Attribute("SomeId").In(someIds)
                };


                var attributes = new Dictionary<string, string>
                                     {
                                         {"RequiresUpdateFromSource", "0"}
                                     };
                uow.Update(toUpdate, attributes);
                uow.SaveChanges();
            }

The SQL output doesn't itterate through the list (tried with array too), it outputs SQL like this...

UPDATE
  my_table
SET
  RequiresUpdateFromSource = '0'
WHERE
  booking_hotels.roomguide_id IN ('System.Collections.Generic.List`1[System.Int32]')

Am I doing something wrong? Since it accepts an array of object I thought it would work passing in an array or list?

Cheers

[quote user="xoozoo.com"]Since it accepts an array of object I thought it would work passing in an array or list?[/quote]

No.  A .NET List<T> is not an array.

What is happening is that In takes params object[] args.  The params keyword means that, as well as passing an object[], you can pass a variable number of arguments (.In(1, 2, 3, 4, 5)) which the C# compiler will package up into an object[] array for you.  That is, the C# compiler will translate .In(1,2,3,4,5) to .In(new object[] { 1,2,3,4,5 }).  Because you are passing a List<T>, which is not an object[], the C# compiler goes, "oh, this must be a 'variable number of arguments' call, where the number of arguments just happens to be 1,' so it wraps it up as .In(new object[] { someIds}).  This results in disaster and suffering as you have seen.

Change your someIds declaration to:

var someIds = new object[] { 1, 2 };

Or if, as seems more likely, you need to build up the collection in a List<T>, use LINQ to Objects to convert the List<T> into an object[]:

var someIds = idList.Cast<object>().ToArray();

This will make the C# compiler go 'okay, I'm being given an object[], so I don't need to go into 'params mode' and wrap it in my own array,' and all will be well.

Hope that makes sense!

Thanks Ivan - I realise a List is not an array - I had also tried an array my example just showed a list - but it was var someIds = new [] {1,2,}; so it was an array of ints rather than objects.

Thanks again for this - excellent, learnt about params object[] args too :)

Cheers